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49 lines
1.8 KiB
Markdown
49 lines
1.8 KiB
Markdown
---
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layout: developer-doc
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title: Operator Resolution
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category: parser
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tags: [parser, operator, resolution]
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order: 5
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---
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# Operator Resolution
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Operator resolution is the process of resolving applications of operators into
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specific nodes on the AST.
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<!-- MarkdownTOC levels="2,3" autolink="true" -->
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- [Resolution Algorithm](#resolution-algorithm)
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<!-- /MarkdownTOC -->
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> The actionables for this section are:
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>
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> - Work out how to ensure that precedence and associativity isn't broken by the
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> macro resolution phase.
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> - Work out how to handle the special case for `,`. We don't want comma to be
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> subject to the variable precedence functionality, as conventional spacing
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> for defining lists goes `[x, y, z]` and that should be allowed without the
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> variable precedence happening.
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> - Work out how to handle the special case for `-`. The expression `-n` should
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> be treated as an application of the unary operator negate, while `- n`
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> should be treated as part of a larger expression (e.g. a section,
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> subtraction).
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> - As Enso has no syntactic marker for the introduction of a lambda, we need to
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> have a special case for `->` so that it has appropriate precedence on its
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> left and right sides. Ideally, `map.fold 0 $ y -> foo $ y` is resolved as
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> `(map.fold 0) $ (y -> (foo $ y))`. This makes writing code much more
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> natural.
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## Resolution Algorithm
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The operator resolution process uses a version of the classic
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[shunting-yard algorithm](https://en.wikipedia.org/wiki/Shunting-yard_algorithm)
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with modifications to support operator sections.
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> The actionables for this section are:
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>
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> - Work out how to formulate this functionality efficiently in rust. The scala
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> implementation can be found
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> [here](../../lib/syntax/definition/src/main/scala/org/enso/syntax/text/prec/Operator.scala).
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